그린 화학을 위한 효과적인 역상 실리카 겔에서의 Pd 촉매 제조

Abstract

최근 불균일 촉매(heterogeneous catalyst)의 활성을 증가시키기 위한 연구가 많이 진행되고 있다. Silica gel은 물리화학적 안정성이 뛰어나고 경제적이어서 다양한 금속을 담지 시킨 촉매연구에 많이 활용되어왔다. 본 연구에서는 가격이 비교적 저렴하고 alkyl기로 end-capping 되어 있는 3-aminopropyl function -alized silica gel (NH2 group loading value : 1 mmol/g)을 지지체로 사용하였다. 또한 이 silica를 이용한 지지체에 서로 다른 두 종류의 리간드를 붙여서 Pd 금속을 담지한 촉매를 개발하였다. 2-Pyridinecarboxaldehyde와 2,2’-bipyridine-4,4’ -dicarboxylic chloride 리간드를 이용하여 합성한 지지체에 Pd(0) nanoparticle을 담지하기 위하여 Pd(OAc)2를 CH2Cl2에 녹여 Pd(II)를 담지하였다. 그 후 NaBH4를 사용하여 Pd(II)를 Pd(0)로 환원하여 반응에 사용될 촉매를 제조하였다. 이 두 촉매를 각각 IPPd(0)@Si, BPPd(0)@Si라고 정하였다. Pd(0)가 담지 된 촉매의 특성은 SEM, TEM, EDX를 이용하여 확인하였다. 담지 된 Pd(0) nanoparticle 크기는 2 ∼ 5 nm로 분포해 있다. IPPd(0)@Si촉매를 이용하여 물속에서 Suzuki-Miyaura Cross coupling 반응을 수행하여 바이아릴 화합물을 합성하였다. 본 촉매를 이용하여 Suzuki-Miyaura Cross coupling 반응의 recycle test를 수행한 결과 모두 90%이상의 높은 수율을 얻을 수 있었다. 또한 IPPd(0)@Si, BPPd@Si 촉매를 이용하여 수소화 반응의 recycle test를 수행한 결과 높은 수율을 얻을 수 있었다. BPPd(0)@Si 촉매의 경우에도 다양한 α,β-unsaturated carbonyl 화합물들을 이용하여 수소화 반응을 보내어 높은 수율을 얻었다. 또한 촉매의 recycle test를 통하여 물속에서 유기용매를 사용하지 않고 유기 반응을 수행함에도 높은 수율로 얻어짐을 확인하였다. |Recently, palladium heterogeneous catalysis has taken over homogeneous one because of the advantages like ease of separation and less contamination. One such heterogeneous catalysts is the one supported on silica that has been widely used due to its inherent properties such as high surface area, good accessibility for organic groups. And chemical, mechanical as well as thermal stability. We present here palladium catalyst using end-capped reverse phase silica as solid support which is in accordance with green chemistry. First catalyst was synthesized by anchoring 2-pyridinecarboxaldehyde ligand on commercially available 3-aminopropyl-functionalized silica gel, followed by Pd metal dispersion. Second catalyst was synthesized by anchoring 2,2’-bipyridine-4,4’-dicarboxyl -ic acid ligand on commercially available 3-aminopropyl-functionalized silica gel, followed by Pd metal dispersion. The catalyst was characterized by XPS, ICP-MS, TEM, etc. The catalysts were tested for Suzuki-Miyaura Cross Coupling reaction and Hydrogenation in water and demonstrated to show excellent yields of products with good recyclability.; Recently, palladium heterogeneous catalysis has taken over homogeneous one because of the advantages like ease of separation and less contamination. One such heterogeneous catalysts is the one supported on silica that has been widely used due to its inherent properties such as high surface area, good accessibility for organic groups. And chemical, mechanical as well as thermal stability. We present here palladium catalyst using end-capped reverse phase silica as solid support which is in accordance with green chemistry. First catalyst was synthesized by anchoring 2-pyridinecarboxaldehyde ligand on commercially available 3-aminopropyl-functionalized silica gel, followed by Pd metal dispersion. Second catalyst was synthesized by anchoring 2,2’-bipyridine-4,4’-dicarboxyl -ic acid ligand on commercially available 3-aminopropyl-functionalized silica gel, followed by Pd metal dispersion. The catalyst was characterized by XPS, ICP-MS, TEM, etc. The catalysts were tested for Suzuki-Miyaura Cross Coupling reaction and Hydrogenation in water and demonstrated to show excellent yields of products with good recyclability.